[edit](mlord wrote his replies while I was writing this)[/edit]

Main power comes from either BB or CB.

Red is always live. It brings power from the switch box to the outlet box, then goes somewhere else.

Black is switched. It is powered by the switch. The fact that line is on the bottom of the switch is not usual, but it should work.


The 30V you're seeing may be caused by induction (the two wires parallel are long enough to act as primary/secondary of a transformer). Try plugging something (night light, lamp) in the switched receptacle and just pull it back enough to measure voltage across prongs. If it's induction, voltage should drop to 0V. It should not cause problem.

A drawing would probably help though.